Dear all,
I have many picaxe projects involving one or several servo motors to control. All in all it is working. At the same time, the operation is somewhat jittery and not as precise, as I would like it to be.
I would like to improve reliability and stability of operation as much as possible. Fine-tune, if you want.
I have several commercially available boards that are performing better than my own creating that I have examined carefully to see what the main differences are.
By far the most stable and trouble-free decoder I have here is based on ATmega 28 pin chip and controls 8 servos. The board has three main areas - power supply, RS323 connection and servo control. The first two are no rocket science, nothing interesting there. The servo control is interesting, however and I would like to discuss it with you.
8 pins from the ATmega go to 8 servo data lines through SN74LS541 (http://www.ti.com/lit/ds/sdls180/sdls180.pdf). I read the data sheet of this thing, but I'm still puzzled as to what it does. The good part is "Hysteresis at Inputs Improves Noise Margins", which sounds like something I'm after. If anyone can help with why and how, would be greatly appreciated.
Another 8 pins go to 8 transistor switches that switch the positive terminals of the servos. The only reason I can imagine this would be for is to prevent the servos from the startup jitter. In other words, you switch the servos on through the micro controller, rather than just with everything else. Or could there be another reason?
Does the above makes sense? I could try and design a servo controller based on picaxe like this. Maybe there already are similar projects out there.
Thank you for your time,
Edmunds
I have many picaxe projects involving one or several servo motors to control. All in all it is working. At the same time, the operation is somewhat jittery and not as precise, as I would like it to be.
I would like to improve reliability and stability of operation as much as possible. Fine-tune, if you want.
I have several commercially available boards that are performing better than my own creating that I have examined carefully to see what the main differences are.
By far the most stable and trouble-free decoder I have here is based on ATmega 28 pin chip and controls 8 servos. The board has three main areas - power supply, RS323 connection and servo control. The first two are no rocket science, nothing interesting there. The servo control is interesting, however and I would like to discuss it with you.
8 pins from the ATmega go to 8 servo data lines through SN74LS541 (http://www.ti.com/lit/ds/sdls180/sdls180.pdf). I read the data sheet of this thing, but I'm still puzzled as to what it does. The good part is "Hysteresis at Inputs Improves Noise Margins", which sounds like something I'm after. If anyone can help with why and how, would be greatly appreciated.
Another 8 pins go to 8 transistor switches that switch the positive terminals of the servos. The only reason I can imagine this would be for is to prevent the servos from the startup jitter. In other words, you switch the servos on through the micro controller, rather than just with everything else. Or could there be another reason?
Does the above makes sense? I could try and design a servo controller based on picaxe like this. Maybe there already are similar projects out there.
Thank you for your time,
Edmunds
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